Radiant plasma source having a gas impervious conical anode



July 4, 1967 w. A. JAATINEN 3,329,365

RADIANT PLASMA SOURCE HAVING A 6A5 IMPERVIOUS CONICAL ANODE Original Filed May 1, 1963 INVENTOR.

WALTER A. JAATINEN his A TTORNEYS.

United States Patent 3,329,865 RADIANT PLASMA SOURCE HAVING A GAS IMPERVIOUS CONICAL ANODE Walter A. Jaatinen, Hackensack, N.J., assignor to Vitro Corporation of America, New York, N.Y., a corporation of Delaware Continuation of application Ser. No. 277,385, May 1,

1963. This application Jan. 19, 1966, Ser. No. 533,104 4 Claims. (Cl. 315-111) This is a continuation of application Ser. No. 77,38 filed May 1, 1963, now abandoned, for Radiant Plasma Source.

This invention relates to radiant sources and more particularly to electric arc configurations capable of generating intense radiant electrical plasmas which may be used as radiant sources in solar simulation devices, arc imaging furnaces, searchlights and other devices which require intense energy sources.

The electric arc configuration, as generally shown in the drawings, consists of a centrally disposed negatively charged cathode surrounded concentrically by a positively charged anode. The cathode has a forward area and at least one tapering sidewall which diverges as it proceeds rearwardly toward the annular frontal surface of the rearwardly disposed anode. This frontal surface of the anode faces the forward area of the cathode which may be sharpened in order to concentrate the negative charge at the cathodes leading point. Between this point and the frontal surface of the anode, in the area adjacent the tapering side surface of the cathode, gas is introduced which is appropriate for use as a high intensity plasma medium.

With the radiation source arranged in this manner, electrical means produce an are between the sharpened end point of the concentrated charge on the cathode and the frontal annular surfaces of the anode. This electric arc thus passes along a path substantially parallel to the tapering side surface of the cathode. The gaseous molecules situated within the conductive path in this region are thus exposed to the high velocity flow of electrons which, in turn, ionize the gas and produce a high intensity radiation.

This invention specifically differs from the prior art and copending application, Ser. No. 188,705 filed on Apr. 19, 1962, now US. Patent No. 3,136,915, in that the ambient atmosphere in which the configuration is operated provides the material which forms the plasma in the electrical discharge region between the cathode and the anode. This solid anode maybe in the shape of a truncated cone or other geometrical configuration and may be both symmetric and concentric with relation to the cathode. As described above, the pointed end of the cathode is located so that it is forward of the frontal surface of the solid anode. By virtue of this displacement, the conduction path or are phenomena between the cathode point and the frontal annular surface of the solid anode are caused to occur spatially to the rear of the cathode point. When this are is operated as a Brennfieckbogen are or burning spot arc, a strong contraction of the column occurs at the cathode, and, as disclosed in copending application Ser. No. 188,705, a sharply defined cathode jet is obtained which is normal to the cathode terminus of the are. This jet of high current density and temperature is a region of high radiant intensity, and in this configuration is a uniquely isolated source of intense radiance.

A second improvement disclosed by this invention overcomes a distinct problem discovered in operating the configuration described in copending application Ser. No. 188,705. It is naturally desirable to obtain stable operation under conditions in which the entire symmetrical anodic terminus is covered by the arc discharge. The

3,329,865 Patented July 4, 1967 establishment of this stable umbrella-type arc is wholly dependent upon the total electrical current input to the arc. In order to maintain this umbrella-arc discharge over the entire anodic terminus area, a minimum operating current is required. In operating under the old configuration in a situation Where the minimum current is not applied to the arc, the discharge tends to fix itself to one part of the frontal surface of the anodic terminus thereby resulting in an unsymmetrical discharge. It is an object of this invention to simulate this umbrella form of electrical arc discharge and thereby achieve stable operating conditions when the total input current is less than minimum stable power levels for the configuration disclosed herein. This may be accomplished by placing or rotating a magnetic field circumferentially about the solid anode in such a manner as to cause the anode terminus of the discharging arc to rotate about the face of the anode. In this manner the anode terminus is distributed equally over the anode face for a given rotational period and, at high rates of rotation, gives the appearace of a uniform symmetrical discharge. The apparatus for establishing a magnetic field may be integral with the high intensity radiation source structure or may be entirely external to this high intensity source.

Other objects and a fuller understanding of this invention may be had by referring to the following detailed description and claim taken in conjunction with the accompanying drawing in which:

FIGURE 1 shows an elevational view in cross section of an embodiment of the invention.

With reference to the drawings, the invention is illustrated as being incorporated into a cylindrical type of radiation source as shown in FIGURE 1 and indicated by reference character 10. As illustrated in detail, the radiation source comprises a cylindrical cathode 11 having a conical portion 12. The side surface 13 of this conical portion 12 tapers divergingly from a forward cathode point 14 to a rearwardly disposed solid anode 15. This solid anode is in the shape of a hollow truncated cone and is shown in FIGURE 1 surrounding cathode 11 but positioned behind conical portion 12. Forward annular surface 16 of solid anode 15 circles cathode 11 and faces cathode point 14 from its rearwardly disposed position.

Separating solid anode 15 from cathode 11 is insulated disc 17 which may be composed of boron nitride. Also connected to anode 15 is water-cooled copper anode holder 18 which is, in turn, connected to a positively charged source 19.

Pressure plug 20 which may also be composed of boron nitride surrounds cathode 11 and insures its separation from solid anode 15. The cylindrical end 21 of a cathode 11 proceeds into recessed portion 22 of pressure plug 20. Within this recess 22 water-cooled copper cathode holder 23 intermittently engages cylindrical end 21 of cathode 11. The other end of holder 23 is connected to a negatively charged source 24.

Surrounding solid anode 15 are electrical coils 26 which are positioned to produce a magnetic field in the area of the anode and which are connected by leads to a separate electrical source.

In operation, ambient gas is introduced into the area immediately adjacent to the tapering side surface 13 of cathode 11. Electrical means 19 and 24 produce an are 25 between positively charged solid anode 15 and negatively charged cathode 11. Electrical are 25 passes between conical point 14 of cathode 11 and annular frontal surface 16 of solid anode 15. A stream of electrons flowing along this conductive path toward the anode surface is approximately parallel to the side surface of cathode 11 and energizes the gas in this region to a substantially high degree.

The umbrella-arc discharge between the cathode point 14 and the entire frontal surface area 16 of anode 15 may be maintained even below minimum current input requirements. When insufficient current is provided for uniform umbrella-type discharge and electrical arc 25 forms a spot-arc at one point on surface 16 of solid anode 15, surrounding electrical coils 26 are activated, and a magnetic field established. With the magnetic field in operation, the spot are 25 is rotated about the concentrically placed forward surface 16 of solid anode 15. The speed of this rotation may be such that the umbrellaarc discharge is simulated.

Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and arrangement of parts, such as variations in the sharpened area of the tapering cathode and variations in the geometric configuration of the anode, may be resorted to without departing from the spirit and scope of the invention as hereafter claimed.

I claim:

1. .Apparatus for providing a high intensity radiation source comprising:

a conical cathode having a forward pointed end facing generally in a forward direction and a tapering side surface diverging behind said forward pointed end, a solid truncated anode cone which is impervious to gas surrounding said conical cathode and positioned behind said tapering side surface of said cathode, said anode having a hollow center and having an annular frontal surface facing in said forward direction and facing fluid located in a region adjacent said tapering side surface of said conical cathode, and electrical means for causing an arc to be formed between said forward pointed end of said conical cathode and said frontal surface of said anode substantially parallel at least in part with said side surface of said cathode, said are being substantially umbrellashaped and forming a zone of high energy concentration adjacent the forward end of the said cathode. 2. Apparatus as defined in claim 1, in which is provided means to establish a magnetic field acting on and rotating the arc discharge to provide when necessary a simulated umbrella-shaped are discharge.

3. Apparatus for generating high intensity radiation comprising a conical pointed cathode on an axis, an annular solid anode impervious to gas concentric with the axis and having an annular frontal surface facing generally in the same direction as the pointed cathode, electrical means to establish an electrical discharge point at a given potential at the point of the cathode and an annular zone of electrical potential higher than the given potential on the frontal surface of the anode, and means retaining the cathode point on the axis relative to the annular frontal surface of the anode to establish an umbrella-shaped arc discharge emanating from the cathode point and terminating at the annular frontal surface, the umbrellashaped arc discharge passing through an ambient atmosphere of ionizable gas located inwardly of the annular frontal surface of the anode and outwardly of the cathode, said electrical means being operative to strike and maintain the umbrella-shaped arc to ionize the gas and produce a high energy plasma jet flowing from a location near the cathode point.

4. Apparatus for generating a high intensity radiation comprising a conical pointed cathode on an axis, an annular solid anode impervious to gas concentric with the axis and having an annular frontal surface facing generally in the same direction as the pointed cathode, electrical means to establish an electrical discharge point at a given potential at the point of the cathode and an annular zone of electrical potential higher than the given potential on the frontal surface of the anode, and means retaining the cathode point on the axis relative to the annular frontal surface of the anode to provide when suitably energized an umbrella-shaped arc discharge emanating from the cathode point and terminating at the annular frontal surface, the umbrella-shaped arc discharge passing through an ionizable gas located inwardly of the annular frontal surface of the anode and outwardly of the cathode, said electrical means being operative to strike and maintain an are from the cathode point to the frontal surface of the anode, and means to establish a magnetic field acting on and rotating the arc discharge with the cathode point as its center of rotation to provide a. simulated umbrella-shaped arc discharge which ionizes the gas and produces a high energy plasma jet flowing from a location near the cathode point.

References Cited FOREIGN PATENTS 20,697 1907 Great Britain.

JAMES W. LAWRENCE, Primary Examiner.

S. D. SCHLOSSER, Assistant Examiner. 

1. APPARATUS FOR PROVIDING A HIGH INTENSITY RADIATION SOURCE COMPRISING: A CONICAL CATHODE HAVING A FORWARD POINTED END FACING GENERALLY IN A FORWARD DIRECTION AND A TAPERING SIDE SURFACE DIVERGING BEHIND SAID FORWARD POINTED END, A SOLID TRUNCATED ANODE CONE WHICH IS IMPERVIOUS TO GAS SURROUNDING SAID CONICAL CATHODE AND POSITIONED BEHIND SAID TAPERING SIDE SURFACE OF SAID CATHODE, SAID ANODE HAVING A HOLLOW CENTER AND HAVING AN ANNULAR FRONTAL SURFACE FACING IN SAID FORWARD DIRECTION AND FACING FLUID LOCATED IN A REGION ADJACENT SAID TAPERING SIDE SURFACE OF SAID CONICAL CATHODE, AND ELECTRICAL MEANS FOR CAUSING AN ARC TO BE FORMED BETWEEN SAID FORWARD POINTED END OF SAID CONICAL CATHODE AND SAID FRONTAL SURFACE OF SAID ANODE SUBSTANTIALLY PARALLEL AT LEAST IN PART WITH SAID SIDE SURFACE OF SAID CATHODE, SAID ARC BEING SUBSTANTIALLY UMBRELLASHAPED AND FORMING A ZONE OF HIGH ENERGY CONCENTRATION ADJACENT THE FORWARD END OF THE SAID CATHODE. 